Radio having adjustable seek sensitivity based on average signal strength and method therefor

ABSTRACT

A tuneable radio and method for automatically adjusting the seek sensitivity alignment for seek operations. The radio has a radio receiver for receiving broadcast radio wave signals, and a tuner adjustable for selecting from a plurality of radio wave signal channels. A detector detects signal strength of the received radio wave signals, and a seek input allows a user to initiate a seek operation to select a signal channel having a signal strength exceeding a seek sensitivity threshold. A controller calculates an average signal value and adjusts the seek sensitivity threshold based on the average value. The controller adjusts the seek sensitivity when it is determined that the radio has travelled beyond a minimum distance.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is one of two applications filed on the samedate, both commonly assigned and having similar specifications anddrawings, the other application being identified as U.S. applicationSer. No. [Docket No. DP-301393], entitled “RADIO HAVING ADAPTABLE SEEKSENSITIVITY CONTROL AND METHOD THEREFOR.”

TECHNICAL FIELD

[0002] The present invention generally relates to electronic radios and,more particularly, to a mobile tuneable radio, such as a car audioradio, having a signal channel seek operation for tuning to signalchannels having sufficient signal strength.

BACKGROUND OF THE INVENTION

[0003] Automotive vehicles are commonly equipped with an AM/FM radio forproviding audio entertainment for the passenger(s) in the vehicle. Audiocar radios are typically packaged with playback devices such as compactdisc (CD) and/or tape cassette players, as well as other audioentertainment devices. AM/FM radios include AM and FM receivers forreceiving amplitude modulated (AM) and frequency modulated (FM) signals,respectively. Also included is a tuner for adjustably selecting amongsta plurality of radio wave signal channels that are generally availableon the commercial airwaves. Many AM/FM radios are programmable to setdesired radio wave channels (frequencies), so that a user may select apreset channel. In addition, conventional AM/FM radios are commonlyequipped with channel seek and scan operations which enables the radioto successively search out those available radio wave channels meeting aminimal signal strength requirement.

[0004] The radio seek operation is performed when a user depresses aseek pushbutton. In response to depressing the seek pushbutton, theradio scans each successive signal channel, in increasing or decreasingorder of the frequency bandwidth, and selects the next received signalchannel having a signal strength greater than a seek sensitivitythreshold. Each depression of the seek pushbutton will tune to the nextreceived signal channel having a signal strength exceeding the seeksensitivity threshold. The scan operation automatically repeats the seekfunction at set time intervals. The seek sensitivity threshold iscommonly fixed by the manufacturer of the radio during a one-time seeksensitivity alignment procedure.

[0005] Automotive radios employing the fixed seek sensitivity thresholdmay be well suited for some users. However, a fixed seek sensitivitythreshold has several drawbacks in that, as the vehicle moves intodifferent geographic regions, the available number of signal channelsand the strength of the radio wave signals may change. The signalstrength of radio wave signals can change dramatically, and somestations may disappear altogether, while other stations becomeavailable. This is especially true when the geographic position of theradio receiver changes in excess of fifty miles. Further, the fixed seeksensitivity threshold may not be adequate for use in certain geographicregions, in which the vehicle be employed. For example, a seeksensitivity threshold that is sufficient for use in urban regions may beinsufficient for use in rural regions where the threshold value mayresult in the reception of too few stations during a seek operation.Contrarily, a lower seek sensitivity threshold that is sufficient foruse in rural regions with fewer available stations may result in theselection of too many signal channels when used in an urban region.

[0006] The decision as to what level of signal strength is listenable issubjective, and may vary based on the concentration of receivable radiostation signals available within the region of use. In areas of fewradio stations, listeners may accept a lower seek sensitivity threshold,and thus noisier signals, than listeners located in a region with ahigher number of radio stations. Accordingly, it is therefore desirableto provide for a tuneable automotive radio that provides a seekoperation to enable a user to select an adequate number of signalchannels.

SUMMARY OF THE INVENTION

[0007] In accordance with the teachings of the present invention, atuneable radio and method are provided for automatically adjusting theseek sensitivity of a radio. The radio has a radio receiver forreceiving broadcast radio wave signals, a tuner adjustable for selectingfrom a plurality of radio wave signal channels, and a signal detectorfor detecting signal strength of the received radio wave signals. A seekinput is provided for initiating a seek operation to seek a radio wavesignal channel having a detected signal strength greater than a seeksensitivity threshold. The radio also has a controller for receiving aplurality of the received radio wave signals and determining an averagevalue. The controller adjusts the seek sensitivity threshold based onthe average value.

[0008] According to the method of the present invention, a method ofautomatically adjusting the seek sensitivity of a radio is provided. Themethod includes the steps of receiving broadcast radio wave signals,selecting from a plurality of radio wave signal channels with a tuner,detecting signal strength of the received radio wave signals,calculating an average value from said received plurality of receivedradio wave signals, and adjusting a seek sensitivity threshold based onthe average value.

[0009] Accordingly, the seek sensitivity of the radio is automaticallyadjusted to provide for enhanced radio station reception for users,particularly for use in automotive vehicles that travel in regions ofvarying radio station concentrations. The radio advantageously allowsfor the seek sensitivity adjustment to increase the seek sensitivitythreshold in regions having higher concentrations of available stationsso as to reduce the number of signal channels that are selected, whiledecreasing the seek sensitivity threshold in regions having lowerconcentrations of available radio stations so as to increase the numberof signal channels that are selected. This allows the radio to adapt toprovide enhanced seek operations.

[0010] These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims and appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will now be described, by way of example,with reference to the accompanying drawings, in which:

[0012]FIG. 1 is a perspective view of an automotive vehicle equippedwith a tuneable AM/FM radio;

[0013]FIG. 2 is a block diagram of the tuneable radio, according to oneembodiment of the present invention;

[0014]FIG. 3 is a graph illustrating automatic gain control (AGC)signals received with the radio and compared with an adjustable seeksensitivity threshold for an FM radio wave bandwidth;

[0015]FIG. 4 is a flow diagram illustrating a routine for setting theseek sensitivity threshold and performing a seek operation with theradio;

[0016]FIG. 5 is a flow diagram illustrating a subroutine for adjustingthe seek sensitivity threshold;

[0017]FIG. 6 is a flow diagram illustrating a routine for setting theseek sensitivity threshold based on GPS position signal information;

[0018]FIG. 7 is a flow diagram illustrating a routine for setting theseek sensitivity threshold based on a continuous travel time count;

[0019]FIG. 8 is a flow diagram illustrating a subroutine for computingthe continuous travel time count for use in the routine of FIG. 7;

[0020]FIG. 9 is a flow diagram illustrating an initalization routine fordetermining the initial seek sensitivity threshold;

[0021]FIGS. 10A and 10B are flow diagrams illustrating a routine foradjusting the seek sensitivity threshold in accordance with the presentinvention; and

[0022]FIG. 11 is a flow diagram illustrating a routine for performing aseek operation using the adjustable seek sensitivity threshold of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] Referring to FIG. 1, an automotive vehicle 10 is shown equippedwith an AM/FM radio 12 which is configured to perform a radio channelseek operation with adjustable seek sensitivity alignment, according tothe present invention. According to the embodiment shown, the radio 12is an AM/FM audio car radio equipped to provide reception of AM and FMradio wave signals available in the coverage region. While the radio isdescribed herein as an audio car radio, it should be appreciated thatthe radio may be employed as a separate stand alone electronic device,such as a portable handheld radio, and may be used in various otherapplications, without departing from the teachings of the presentinvention.

[0024] The audio car radio 12 may be mounted on the dash of the vehicle10 according to a conventional car radio installation. The car radio 12shown is an AM/FM radio equipped with audio playback devices, includingan audio tape player and a compact disc (CD) player. Extending from theradio face plate is a human-machine interface (HMI) key matrix with aplurality of manually operable controls. Included in the manual controlsis an “AM/FM” pushbutton switch 18 for selecting either of the amplitudemodulation (AM) signal band and the frequency modulation (FM) signalband. The manual controls further include a “SEEK” pushbutton switch 20that is manually depressible to initiate a radio channel seek operationaccording to the present invention. The “SEEK” pushbutton switch 20performs a seek operation when momentarily depressed, and furtheractivates the scan operation when continuously depressed for an extendedtime period, such as two seconds. Also included in the controls arepushbutton switches 17 and 19 for selecting the audio tape player and CDplayer, respectively. The manual controls are easily accessible by thedriver or passenger(s) in the vehicle 10.

[0025] The vehicle 10 is further shown equipped with a radio antenna 14for receiving broadcast radio wave signals. Radio antenna 14 is capableof receiving AM and/or FM broadcast radio wave signals. Further, aglobal positioning system (GPS) receiver/antenna 16 is shown mounted onthe roof of the vehicle 10, and is exposed to GPS radio wave signals.

[0026] Referring to FIG. 2, the AM/FM audio car radio 12 is shown havingan RF bandpass filter 22 connected to antenna 14 for passing receivedradio wave signals in the AM and FM frequency bandwidths, and rejectingother signals. The antenna 14 and RF bandpass filter 22 operates as areceiver to receive radio wave signals. The audio car radio 12 alsocontains an RF amplifier 24, a mixer 26, an intermediate frequency (IF)amplifier and bandpass filter 28, and an S-meter signal detector 30. TheS-meter signal detector 30 senses the signal strength amplitude of theradio wave signals of each tuned signal channel and generates anautomatic gain control (AGC) signal in response thereto. The AGC signalis input as a feedback to the IF amplifier and bandpass filter 28, andis also input to an analog-to-digital converter 38. The output of theanalog-to-digital converter 38, in turn, is input to a microprocessor40. The microprocessor 40 generates an output signal which is input to adigital voltage controlled oscillator (VCO) 44, which, in turn, providesan input to the mixer 26 to tune the radio 12 to one of a plurality ofavailable radio frequency signal channels. Together, the mixer 26,digital VCO 44, microprocessor 40, detector 32, A/D converter 38, and IFamplitude bandpass filter 28 provide an AM/FM radio tuner for tuning toselected radio frequency signal channels.

[0027] The microprocessor 40 receives input signals from the GPSreceiver 16, a mileage data (vehicle computer) signal 46, and a controlsignal from the seek pushbutton 20. The microprocessor 40 stores theinputs in memory 42. Memory 42 also stores routines for controllingradio operations including various routines for controlling seeksensitivity threshold adjustments, according to the present invention.According to one embodiment of the present invention, themicrocontroller 40 determines when to update the seek sensitivitythreshold based on distance travelled as determined by the GPS receiver16. According to another embodiment, the microprocessor 40 determineswhen to update the seek sensitivity threshold based on mileage datasignal 46 and an elapsed time period of vehicle travel. According toanother aspect of the present invention, the microprocessor 40 adjuststhe seek sensitivity threshold based on a determined average signalstrength of received signals.

[0028] The radio 12 further includes a baseband filter 32 and an audioamplifier 34 for generating an output audio signal. In addition, atransistor 48, in response to a control signal from the microprocessor40, provides mute control to mute the audio output. The radio 12 isconnected to one or more audio speakers 36 as is well-known forgenerating audio sound in response to output signal 34.

[0029] According to well-known GPS operations, the GPS receiver 16receives GPS radio wave signals via a GPS receiving antenna. The GPSradio wave signals are emitted from existing GPS satellites. Aconstellation of multiple high altitude GPS satellites currently existin Earth orbit and are available to provide continuous worldwideposition (location) fixes in all types of weather conditions. The GPSreceiver 16 may include a conventional built-in processing unit andmemory for processing the GPS radio wave signals to determine thelatitude and longitude position coordinates of the current location, aswell as determining the current direction of travel and speed of thevehicle.

[0030] More specifically, the GPS receiver 16 continuously receivesradio wave signals from the GPS antenna and determines accurate positioncoordinates which identify the location of the received signals. Thisdetermination includes calculating the distance from various satellitesto determine a location relative thereto. By measuring the currentsignals sent by the GPS satellites and knowing orbital parameters of thesatellites, the GPS receiver is able to determine the location thereofand generate longitude and latitude position coordinates which identifythe location of the received signals. Given the received GPS signals,the latitude and longitude position coordinates of the GPS receiver aredetermined by computing distance from each of several GPS satellitescurrently visible to the receiver 16 by direct line-of-sight. Distanceis determined by precise computation of the time required for radiosignals to travel from the GPS satellite to the GPS receiver 16.Combined with precise information about the satellites' locationsrelative to the Earth, precise latitude and longitude positioncoordinates are computed. GPS is widely known and should be understoodto those skilled in the art as a means for providing accurate locationinformation. Further, it should be appreciated that other forms oflocation determining devices, other than GPS, could be employed now andin the future to provide location information.

[0031] Referring to FIG. 3, one example of AGC voltage signal strengthvalues measured at various radio wave signal channels in the FMfrequency bandwidth is illustrated therein. A first seek sensitivitythreshold is shown by line 52 which, according to one embodiment, may beset at the factory by the radio or vehicle manufacturer. It should beappreciated that the present invention advantageously adjusts the seeksensitivity threshold to a new seek sensitivity threshold, such as line50, in accordance with the present invention. With the seek sensitivitythreshold set at line 50, only those radio wave signal channels aboveline 50, as indicated by signals 54, will be detected during a seekoperation, as well as during a scan operation. Those channels havingsignal strength values below the seek sensitivity threshold 50,identified as signals 56, will be ignored during a seek or scanoperation. It should be appreciated that the present invention adjuststhe seek sensitivity threshold so as to limit the number of signalchannels detected in regions having a large number of available radiostation channels, and may be lowered to select an increased number ofsignal channels in regions having a lower number of available radiostation channels.

[0032] The control routines for adjusting the seek sensitivity thresholdand performing a seek operation according to the present invention aregenerally illustrated in FIGS. 4-11. More particularly, the routinesshown in FIGS. 4-8 determine when a seek sensitivity thresholdadjustment may be made based on a GPS measured travel distance or anestimated travel distance of the vehicle. The routines shown in FIGS.9-11 provide an adjustment of the seek sensitivity threshold based on anaverage signal strength of the received radio wave signals.

[0033] Referring to FIG. 4, a seek routine 60 is illustrated therein fordetermining whether to perform a seek sensitivity alignment procedure toadjust the seek sensitivity threshold, and further for selecting asignal channel during a seek operation. Routine 60 begins at step 62 andproceeds to decision step 64 to check if GPS data is available. If GPSdata is available, routine 60 proceeds to decision step 66 to determineif the current GPS determined location (i.e., position) deviates fromthe last GPS location GPS (A) in excess of an amount X and, if so,proceeds to step 68 to mute the audio, and then proceeds to step 70 tojump to the stop align subroutine. The stop align subroutine, which isdiscussed herein in connection with FIG. 5, determines a new seeksensitivity threshold, also referred to as the stop threshold. If thecurrent GPS determined location has not deviated from the last locationGPS (A) in excess of distance X, step 66 proceeds directly to step 76.Referring back to step 64, if the GPS data is not available, routine 60proceeds to decision step 72 to check if the continuous travel timecounter (CTTC) is greater than a time count value Y and, if so, proceedsto step 68 to mute the audio, and thereafter proceeds to step 70 to jumpto the stop align subroutine. If the continuous travel time counter isnot greater than time count Y, routine 60 proceeds to step 74 to mutethe audio output and then proceeds to step 76. It should be appreciatedthat the continuous travel time counter is an alternate means toestimate if the vehicle may have travelled a great enough distance suchthat it would be advantageous to readjust the seek sensitivitythreshold.

[0034] In step 76, the seek routine 60 sets the current radio frequencyas the start frequency, and then proceeds to step 78 to tune to the nextfrequency. Next, decision step 80 determines if the automatic gaincontrol signal is greater than the stop threshold, (i.e., seeksensitivity threshold). If the automatic gain control signal is notgreater than the stop threshold, routine 60 proceeds to decision step 82to determine if the current frequency has returned to the startfrequency and, if not, returns to step 78. If the automatic gain controlsignal is greater than the stop threshold, or if the current frequencyhas returned to the start frequency, seek routine 60 proceeds to stop atthe current frequency in step 84. Accordingly, a radio channel isselected in step 84. Once the radio channel is selected, the audiooutput is unmuted in step 86 and, the seek routine is stopped in step88.

[0035] The stop align subroutine 90 is illustrated in FIG. 5. Subroutine90 begins at step 92, and proceeds to step 94 to set the currentfrequency as the start frequency. Next, in step 96 the radio is tuned tothe next successive frequency (channel) and then the measured signalstrength data is stored in an array as the stop threshold. In decisionstep 100, subroutine 90 determines if the current frequency has returnedto the start frequency and, if not, returns to step 96. Otherwise,subroutine 90 proceeds to step 102 to perform a weighted average of thesignal strength value meeting a minimum signal strength level. It shouldbe appreciated that a weighted average value is preferably determinedbased on only signals meeting the minimum signal strength level, such asa minimum factory setting. Once the weighted average value isdetermined, decision step 104 determines if the average value is above aminimum AGC level. If the average value is not above the minimum AGClevel, the average value is set equal to the factory minimum in step106, and is then stored as the new stop threshold in step 108.Otherwise, if the average value is above the minimum AGC level, theaverage value is stored as the new stop threshold in step 108.

[0036] Once the stop threshold value has been determined, subroutine 90proceeds to decision step 110 to determine if a GPS input is availableand, if not, proceeds to step 114 to return to the calling routine. IfGPS input data is available, subroutine 90 proceeds to step 112 to storethe current GPS location as GPS (A), and then returns to the callingroutine in step 114. Accordingly, subroutine 90 determines a weightedaverage value and automatically adjusts the seek sensitivity thresholdbased on a weighted average value.

[0037] Referring to FIG. 6, a background GPS alignment routine 120 isillustrated therein. Routine 120 begins at step 122 and proceeds to getthe current GPS location in step 124. Next, in decision step 126,routine 120 determines if the current GPS location deviates from thelast stored GPS location in excess of a distance X and, if not, proceedsto step 134 to exit the background GPS alignment routine. If thedistance between the current GPS location and the last stored GPSlocation exceeds distance X, routine 120 proceeds to decision step 128to determine if the tuner is inactive. If the tuner is active (i.e.,on), routine 134 exits in step 134. If the tuner is inactive (i.e.,off), routine 120 proceeds to step 130 to maintain the current mode ofthe radio, such as the CD player or the tape player, for example.Thereafter, in step 132, routine 120 jumps to the stop alignmentsubroutine to determine a new seek sensitivity threshold, and then exitsthe background GPS alignment routine in step 134. Accordingly, the seeksensitivity threshold is adjusted when the tuner is not active, such aswhen the radio is operating in a playback mode. By requiring that thetuner be inactive, the tuner can be employed to scan all signal channelsto acquire the signal strength of each channel.

[0038] A background continuous travel time counter alignment routine 140is illustrated in FIG. 7. Routine 140 begins at step 142 and proceeds tostep 144 to get the current CTTC value. Next, in decision step 146,routine 140 checks to see if the current CTTC value is greater thanvalue Y and, if not, exits the routine 140 in step 156. If the currentCTTC value exceeds value Y, routine 140 proceeds to decision step 148 todetermine if the tuner is inactive and, if not, exits routine 140 instep 156. If the tuner is inactive, routine 140 proceeds to step 150 tomaintain the current mode of the radio, such as the CD player or thetape player, for example. Thereafter, in step 152, routine 140 goes tothe step align subroutine to determine a new seek sensitivity threshold.Next, routine 140 resets the CTTC value to zero in step 150 and exitsroutine 140 in step 156. Accordingly, the seek sensitivity threshold isadjusted when the tuner is not active, such as when the radio isoperating in a playback mode. By requiring that the tuner be inactive,the tuner can be employed to scan all signal channels to acquire thesignal strength of each channel.

[0039] A continuous travel time counter routine 160 is illustrated inFIG. 8. Routine 160 begins at step 162 and proceeds to decision step 164to check if the odometer reading is increasing. If the odometer readingis not increasing, indicating that the vehicle is not in motion, routine160 then checks for whether R minutes have elapsed in decision step 166and, if so, resets the CTTC value to zero in step 168, and then returnsto decision step 164. If R minutes have not elapsed, routine 160 returnsto step 164 without resetting the CTTC value to zero. If the odometerreading is increasing, indicative that the vehicle is moving, routine160 proceeds to step 170 to increase the continuous travel time counterby one count increment per minute. The CTTC value is then saved inmemory in step 172, and is then employed in routine 140 as describedabove.

[0040] Accordingly, the seek sensitivity threshold alignment of thepresent invention advantageously provides for an adjustable seeksensitivity threshold that may vary depending on the signal strength andnumber of radio station signals available. The seek sensitivitythreshold is adjusted when the vehicle may have travelled a sufficientdistance as determined by GPS data or odometer and time countinformation. The seek sensitivity threshold alignment preferably occurswhen the tuner is inactive, such as when the radio is operating in aplayback mode, such as the cassette player or CD player. By requiringthat the tuner be in an inactive mode, the determination and adjustmentof a seek sensitivity threshold does not interrupt the tuner andtherefore the audio radio mode of operation. Accordingly, the seeksensitivity threshold alignment allows for a more controlled number ofstations to be received during a radio seek operation.

[0041] Referring to FIG. 9, a seek threshold initialization routine 200is shown for initially determining the seek sensitivity threshold whenthe vehicle is first started following a power disruption. The routine200 begins at step 202 and proceeds to decision step 204 to determine ifvalid AGC data is stored in memory. If valid AGC data is stored inmemory, the routine 200 assumes an initial seek sensitivity threshold isalready present and proceeds to the new seek routine in step 206.Otherwise, routine 200 proceeds to step 208 to initially set the stopthreshold equal to zero. Thereafter, in step 210, routine 200 incrementsto the next valid radio frequency, and then proceeds to decision step212 to check whether the tuner has returned to the start frequency. Oncereturning to the start frequency, routine 200 proceeds to step 214 tomeasure the AGC value, and then proceeds to decision step 216 to checkif the AGC value is in the top five values of signal strength and, ifnot, returns to step 210. If the AGC value is in the top five values ofsignal strength, routine 200 proceeds to step 218 to store the frequencyand AGC value in memory, and overrides those values in memory that arenot in the top five signal strength values. Thereafter, routine 200returns to step 210. Once returning to the start frequency, routine 200proceeds to step 220 to calculate an average AGC value based on the topfive values, and then proceeds to step 222 to store the average AGCvalue as the stop threshold, before proceeding to step 224 to go to thenew seek threshold routine. If desired, the average AGC value can beweighted.

[0042] Turning to FIGS. 10A and 10B, the new seek threshold routine 230is illustrated therein. Routine 230 begins at step 232 and proceeds todecision step 234 to determine if at least T minutes have elapsed sincethe last seek operation and, if not, proceeds to the seek routine instep 236. If T minutes have elapsed, routine 230 proceeds to step 238 totune to the next frequency, and then measures the AGC value and adds theAGC value to the average value in step 240. The average value is thensaved as new stop in step 242. In decision step 244, routine 230 checksfor a return to the start frequency and, if the current frequency is notequal to the start frequency, returns back to step 238 to select thenext frequency. Once routine 230 returns to the start frequency, step246 checks to see if the new stop is within predefined limits, such asthose set by the factory. If the new stop is not within the predefinedlimits, routine 230 proceeds to the seek operation routine in step 248.If the new stop is within the predefined limits, routine 230 sets a dBchange equal to the absolute dB difference of new stop minus stopthreshold, in step 250. In decision step 252, a decision of whether thedB change is less than Z dB is determined. If the dB change is less thanZ dB, routine 230 proceeds to the seek routine in step 154. Otherwise,routine 230 proceeds to decision step 256 to check if the new stop isless than the stop threshold. If the new stop is less than the stopthreshold, the stop threshold is decreased by the amount of the dBchange in step 262. Contrarily, if new stop is not less than the stopthreshold, the stop threshold is increased by the amount of the dBchange in step 258. Following the increase or decrease in stopthreshold, routine 230 proceeds to the seek operation routine, in step260.

[0043] The seek operation routine 270 is illustrated in FIG. 11. Theseek operation routine begins at step 270 and proceeds to set thecurrent frequency as the start frequency in step 274. Next, in step 276,the radio tunes to the next frequency, and then proceeds to decisionstep 278 to determine if the AGC value is greater than the stopthreshold and, if so, stops at the frequency in step 282. If the AGCvalue is not greater than the stop threshold, routine 270 proceeds tostep 280 to check for a return to the start frequency and, if not,returns to step 276. Once the channel selection has returned to thestart frequency, routine 270 proceeds to step 282 to stop at thatfrequency. Thereafter, the audio output is unmuted in step 284 prior toproceeding to end the seek operation routine in step 286.

[0044] Accordingly, the routines in FIGS. 9-11 advantageously calculatean average AGC value, and adjusts the seek sensitivity threshold basedon the average value. The adjustable seek sensitivity threshold is thenemployed during a radio seek operation. By doing so, the number of radiostation channels selected during a seek operation may be more suitableto the user.

[0045] While the present invention has been described in connection withan AM/FM audio car radio 12 according to the preferred embodiments, itshould be appreciated that the present invention may be applied to othertypes of radios for receiving various types of information broadcast invarious radio band frequencies, without departing from the spirit of thepresent invention. For example, the radio could be used to automaticallytune to NOAA weather band broadcast signals which typically range from162.400 to 162.550 kHz.

[0046] It will be understood by those who practice the invention andthose skilled in the art, that various modifications and improvementsmay be made to the invention without departing from the spirit of thedisclosed concept. The scope of protection afforded is to be determinedby the claims and by the breadth of interpretation allowed by law.

1. A tuneable radio having an adjustable seek sensitivity, said radiocomprising: a radio receiver for receiving broadcast radio wave signals;a tuner adjustable for selecting from a plurality of radio wave signalchannels; a signal detector for detecting signal strength of thereceived radio wave signals; a seek input for initiating a seekoperation to seek a radio wave signal channel having a detected signalstrength greater than a seek sensitivity threshold; and a controller forreceiving a plurality of said received radio wave signals anddetermining an average value, said controller adjusting said seeksensitivity threshold based on said average value.
 2. The radio asdefined in claim 1, wherein said controller determines an initial seeksensitivity threshold for use as the seek sensitivity threshold byreceiving a predetermined number of received radio wave signals havingthe highest detected signal strength and computing an initial averagesignal strength value of the predetermined number of received radio wavesignals.
 3. The radio as defined in claim 2, wherein said initial seeksensitivity threshold is set equal to said initial average value.
 4. Theradio as defined in claim 2, wherein said initial average signalstrength value is computed based on five to ten received radio wavesignals.
 5. The radio as defined in claim 1, wherein said average signalstrength value is computed based on five to ten received radio wavesignals.
 6. The radio as defined in claim 1, wherein said seeksensitivity threshold is adjusted proportional to the change in averagesignal strength value.
 7. The radio as defined in claim 1, wherein saidseek input comprises a pushbutton.
 8. The radio as defined in claim 1,wherein said tuneable radio is located on a movable vehicle.
 9. Theradio as defined in claim 8, wherein said radio is a car radio.
 10. Amethod of adjusting seek sensitivity in a tuneable radio, said methodcomprising the steps of: receiving broadcast radio wave signals;selecting from a plurality of radio wave signal channels with a tuner;detecting signal strength of the received radio wave signals;calculating an average value from said received plurality of receivedradio wave signals; and adjusting a seek sensitivity threshold based onsaid average value.
 11. The method as defined in claim 10 furthercomprising the step of determining an initial seek sensitivity thresholdfor use as the seek sensitivity threshold by determining an average of apredetermined number of the received broadcast radio wave signals havingthe greatest detected signal strength.
 12. The method as defined inclaim 10 further comprising the step of initiating a seek operation toseek a radio wave signal channel having a detected signal strengthgreater than a seek sensitivity threshold.
 13. The method as defined inclaim 12, wherein said step of initiating the seek operation comprisesdepressing a pushbutton.
 14. The method as defined in claim 10, whereinsaid step of calculating an average value comprises computing an averagesignal value based on five to ten received radio wave signals.
 15. Themethod as defined in claim 10, wherein said step of adjusting the seeksensitivity threshold comprises actual performance of the change in theaverage signal strength value.
 16. The method as defined in claim 10,wherein a tuneable radio is located on a movable vehicle.
 17. The methodas defined in claim 16, wherein said radio is a car radio.